Within high voltage applications it is known in the art to provide corona shields of an electrically conductive material, usually metal, in geometric and electric connection to a high voltage conductor or other high voltage equipment. By distributing the electrical charge over the increased surface area of the shield, the maximum electrical field strength is reduced, thereby reducing the risk of corona discharge.
One disadvantage with such an arrangement is that due to the large curvature and geometrical extension, a zone with relatively high and homogenous electrical field is created. This enables propagation of discharges that can be triggered by small temporary disturbances, such as insects, large dust particles, etc. When high voltages are applied, particularly DC, it has been observed that this mechanism can causes breakdown at voltages which are significantly lower than is expected from conventional design rules.
International application with the publication number WO 2007/149015 discloses providing a resistor between the shield and a valve group in a high voltage direct current application.
While this resistor reduces the risk of such breakdown, it adds to the complexity of a corona shield.